1. Field of the Invention
The present invention relates to an arrangement of determining a latest revision level of each of a plurality of plug-in boards, and more specifically to such an arrangement wherein a latest revision level of each plug-in board is manually set using a number generator mounted on the board. Further, the present invention relates to an arrangement of determining whether or not a current revision level of each of a plurality of plug-in boards is confined within an allowable revision level range.
2. Description of the Prior Art
A digital data processing system, such as a computer, is normally provided with a passive receptacle or sockets into which edge connectors of a plurality of plug-in boards are inserted. Such a passive receptacle is sometimes called a backplane. The plug-in boards are I/O (Input/Output) boards, CPU (Central Processing Unit) boards, Memory boards, etc.
Plug-in boards are independently subject to revisions to improve performance, lower cost, etc. It follows that the revision levels of the boards actually plugged into the backplane of the system may differ with different plug-in boards. Consequently, it is necessary for a person in charge of maintenance (for example) of the system to know which revision level is available for the system in terms of each of the boards to be inserted. To this end, it is vital for the person to have a complete list of revision levels of the plug-in boards which are available.
One known approach to recording the current revision level on a board, is to stamp the current revision level mark on the board. However, it is often the case that the stamped revision level mark is difficult to be visible from the outside when inserted into the system structure due to components mounted on adjacent boards. Accordingly, it is required to pull out the board from the receptacles for ascertaining the stamped revision level. Further, when one or more components of a board are replaced and revised, the old stamped mark is awkwardly erased and a new revision level should be stamped.
Another known approach to determining the revision levels of the boards is to provide each plug-in board with a ROM (read only memory) into which the current revision level of the board is written each time the board is This approach is advantageous in that the revision levels of the plug-in boards can be monitored by a service processor using a display thereof. However, even if one component is revised, it is necessary to rewrite the contents of the ROM. Further, the revision level is electrically recorded in the ROM and thus it is undesirably impossible to visually perceive the revision level from the outside.